From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27E85C10F0E for ; Fri, 12 Apr 2019 13:08:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ECD8B20818 for ; Fri, 12 Apr 2019 13:08:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726772AbfDLNIv (ORCPT ); Fri, 12 Apr 2019 09:08:51 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:60656 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726714AbfDLNIv (ORCPT ); Fri, 12 Apr 2019 09:08:51 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F1E35374; Fri, 12 Apr 2019 06:08:50 -0700 (PDT) Received: from [0.0.0.0] (e107985-lin.cambridge.arm.com [10.1.194.38]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9889C3F718; Fri, 12 Apr 2019 06:08:49 -0700 (PDT) Subject: Re: [RFC 5/6] Improvise cgroup interface for classifying jitter from WOF tasks To: Parth Shah , linux-pm@vger.kernel.org References: <20190322060621.27021-1-parth015@linux.vnet.ibm.com> <20190322060621.27021-6-parth015@linux.vnet.ibm.com> From: Dietmar Eggemann Message-ID: <8de36526-806a-810f-9f5e-393dddb523be@arm.com> Date: Fri, 12 Apr 2019 15:08:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190322060621.27021-6-parth015@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 3/22/19 7:06 AM, Parth Shah wrote: [...] > @@ -6236,7 +6259,15 @@ static int select_non_idle_core(struct task_struct *p, int prev_cpu) > struct cpumask *cpus = &highutil_task_mask_copy; > int core, smt; > > - cpumask_copy(cpus, highutil_task_cpu_mask); > + /* > + * Prefer jitters to be pulled on core occupying WOF tasks > + * If such tasks are not running then use long code path to find > + * non-idle core with spare capacity > + */ I'm struggling to grasp what you mean by ' ... long code path to find non-idle core with spare capacity' here? We're here in: select_task_rq_fair()->__select_idle_sibling()->select_non_idle_core() What is the 'long code path'? In case select_non_idle_core() can't find a CPU, select_idle_sibling() is called but IMHO that's the original fastpath operating on the LLC domain. It can't be the slow path find_idlest_cpu() because that's only called in case __select_idle_sibling() isn't called. [...]